DIY hot precision knife

I came across this idea from an internet hack. It is basically putting a xacto knife blade into a soldering iron to cut plastic.
The real benefit of this is that it can cut thicker objects and ones that you can't get either a Dremel with cutting wheel in, or a razor saw. And for stuff that is too thick to score and snap.
The blade itself is 6mm across, so you need a soldering iron with a tip piece diameter of at least that. I started with a 25w iron, as I picked it up for free with a stuffed tip, but it was too small, would have to cut down the blade shank, which would be a nuisance.
I then had a fairly cheap 80w iron with a 7mm tip shank diameter.

First step is to remove the tip and find a hex head bolt of the right diameter and length. I used a mild steel one, brass would have been better, but I didn't have one. Just really didn't want a stainless or a high tensile one.
Then need to cut a slit in the bolt from the head down into the bolt thread to hold the blade. It is better if the bolt is just narrower than the blade shank so the grub screw can hold onto the xacto blade.
Hacksaw time!

I had to make a new grub screw as the existing one did not have enough reach.
Assemble it all and you have a precision hot knife.
In my case I was using it to cut the bogie mount coupler shanks off these bogies. Often this sort of bogie just pops out, but not these ones. Just got to be careful not to melt anything important.

Cheers
Tony